1. Field of the Invention
The present invention relates to a wireless communication system.
2. Description of the Related Art
In order to satisfy an increasing demand for wireless data traffic, wireless communication systems are developing to support a higher data transmission rate. The 4th Generation (4G) system, which is starting to be commercialized, has been developed mainly to improve spectral efficiency in order to increase a data transmission rate. However, it has become difficult to satisfy an explosively-increasing demand for wireless data traffic solely by the spectral efficiency improvement technology.
As a scheme for addressing the above problem, there is a scheme for using a very wide frequency band. A frequency band used in the current mobile cellular system is generally lower than 10 GHz, and it is very difficult to secure a wide frequency band. There is therefore a need to secure broadband frequencies in a higher frequency band. However, as an operation frequency band for wireless communication becomes higher, a propagation path loss increases. Thus, a wave propagation distance decreases, and a service coverage area decreases accordingly. Beamforming is a technology for addressing this problem, that is, for reducing a propagation path loss and increasing a wave propagation distance.
In general, beamforming concentrates a wave propagation region in a specific direction by using a plurality of antennas, or increases the directivity of reception sensitivity in a specific direction. Herein, a group of a plurality of antennas may be referred to as an antenna array, and each antenna included in the antenna array may be referred to as an array element. The antenna array may be configured in various types such as a linear array and a planar array. When beamforming is used, a transmission distance is increased by an increased signal directivity and a signal is hardly transmitted in directions other than the direction of directivity. Therefore, an interference caused by other signals is greatly reduced. On the other hand, since the multipath characteristic of a channel is reduced due to beamforming, it is difficult to support transmission diversity.
Thus, in applying beamforming, it is preferable to determine whether to perform beamforming in consideration of the communication environment and channel characteristics, or perform a suitable type of beamforming. What is therefore desired is an alternative method for supporting and operating beamforming schemes with different propagation characteristics in wireless communication systems.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present invention.